This invention is directed to a clamp for gripping and displacing flexible members generally made of filamentary material, such as flexible cables, bars or "snakes" which are used to pull cables into cable-protective conduits.
The clamp of this invention includes a clamp body having a longitudinal elongated groove of a generally U-shaped transverse cross-sectional configuration within which is at least partially received the flexible member. The handle is pivotally connected to the clamp body and can be moved to a position in which a portion of the flexible member is clamped between the handle and the clamp body.
In the particular technical field to which the present invention is directed it is necessary to pull cables of electrical wires into cable-protective conduits or sheaths. Cables or wires which are defective must also be removed from cable-protective sheaths and exchanged by new wires or cables, and such new wires or cables are pulled into the cable-protective conduits. The cable-protective conduits are necessarily empty but may have additional wires therein, and the presence of such additional wires at times makes it difficult to pull new wires into the cable-protective conduits. Furthermore, since the cable-protective conduits or pipes are, as a rule, accessible only at a few places along the length thereof, for instance at switch or junction boxes and at outlets, the substantial distances over which the wires and cables must be pulled tends to create inherent failures as efforts are made at pulling the cables and wires into/through the cable-protective conduits. Most times it is necessary to utilize accessory devices to avoid such failures, as, for example, the utilization of flexible members, bars or snakes which on the one hand can adapt to any curvature to the in-place protective conduits but which on the other hand possess enough compressive strength and resistance to kinking that they can be inserted over sufficient lengths by compressive forces (pushing) up to distances of 25 meters into the cable-protective conduits. Once the flexible member/bar has been so inserted, the cable/wire which is to be pulled through the cable-protective conduit is connected to the flexible member and when the latter is pulled back, the electrical cable or wire is then drawn into the cable-protective conduit. Accordingly, it is necessary to provide a clamp which can grip the flexible member or bar as it is pushed into and through the cable-protective conduit and which can also then be pulled back through the cable-protective conduit after electrical wires/cables have been attached thereto.
From a practical standpoint it is extremely laborious to manually push and pull such flexible bars, cables or "snakes" particularly when they are comparatively slender and must be inserted over considerable lengths (25 meters and more) into and through cable-protective conduits and, of course, thereafter withdrawn in the opposite direction together with the electrical wires or cables attached therethrough. Such flexible members readily slip if manually grasped and it is virtually impossible to apply high displacement forces thereto. It has become the tendency for craftsman to wrap these flexible bars, members or "snakes" around one's wrist, elbow or underarm several times (or in other similar manners) attempt to increase one's grip thereof. Aside from the danger of injury to the craftsman/operator, there is also the further risk of excessively bending or kinking the flexible bar or "snake" or otherwise damaging the same causing loss of its compressability and its resistance to kinking.
A conventional clamp is disclosed in French Pat. No. 23 86 168 in which the pulling of electrical cables is facilitated. In this known design the clamp includes a clamp body having one jaw and a longitudinal slot, a handle and a lever arm, and the lever arm carries a second clamping jaw which is appropriately operated to clamp an electrical cable between the two jaws when the handle is pulled. This clamp permits the cable to be moved in only one direction, namely, in the pulling direction of the handle because when the handle is moved in an opposite direction, the lever system separates two clamped jaws. Furthermore, because the described levers and articulated connections are accessible from the exterior, these create a practical area of danger/injury to the operator. Furthermore, the compression applied by the two jaws depends on the traction exerted on the handle and the applied traction does not coincide with the direction of pull of the cable clamped therebetween. Accordingly, because of this off-set there is in actual operation a stepwise pull of the electrical cable which causes it to be undesirably and easily kinked.
Another conventional clamp is disclosed in German Pat. No. 34 16 652 which had a longitudinal slot open on one side within which a flexible member can be inserted. A clamping strip is located inside a clamping body of the clamp and can be displaced toward the longitudinal slot to clamp the flexible member therein. In this case the clamp body consists of two mutually connected plates between which there is located the clamping strip which in a central region thereof remote from the slot includes a cam against which rests a lever pivoted between associated plates. The free end of this lever rests against the inside of a pivoted handle which when actuated causes the lever to press against the cam of the clamping strip to move the latter into its clamping position. This clamp is quite practical, although the practicality depends upon it being constantly used to justify the comparatively high manufacturing costs thereof.